This disclosure relates to test and measurement devices, and in particular, to a distributed time-interleaved acquisition RF triggering method and system.
Traditionally, test and measurement instruments such as spectrum analyzers and vector analyzers have had minimal triggering capabilities. Mixed-Domain Oscilloscopes (MDOs) represent a new product category of test and measurement devices, which integrate many of the spectral acquisition, triggering, and display capabilities of Real-Time Spectrum Analyzer (RTSA) products with the functionality of traditional oscilloscope products. In addition to supporting time domain features of traditional oscilloscopes and frequency domain features of RTSAs, the MDO products enable cross-correlation between both domains for acquisition, triggering, display, and analysis functions.
In such newer types of products, the RF input signal is digitally down-converted to produce I (in-phase) and Q (quadrature) baseband component information from the RF signal. More specifically, the RF signal is numerically multiplied with sine and cosine components of a numerically controlled oscillator (NCO), thereby generating the demodulated baseband I and Q component information, which contains all of the information present in the original RF signal. The trigger system can then trigger on criteria associated with the IQ baseband component information.
In conventional oscilloscopes, time-interleaved acquisition is an approach for building test and measurement device acquisition systems with scalable sample rate and bandwidth, and to extend acquisition systems beyond the capabilities of individual analog to digital converter (ADC) and/or digitizer components. For example, FIG. 1 shows a conventional example of a time-interleaved acquisition system 100 used in oscilloscopes. A high-bandwidth sampler such as a track and hold component 105 is used to distribute sampled versions of the input signal 130 to multiple ADCs 110 with appropriate offsets in sampling time, based on the aggregate sample rate of the acquisition system.
A digitizer component such as component 115 is then used to process the incoming samples and store them in acquisition memory 120. The digitizer component 115 is a type of building block for acquisition, triggering, display, and analysis in an oscilloscope device. There is usually some form of interconnect between the different digitizer components for further processing of time-interleaved data samples, which results in a coherent waveform 125 at the full sample rate of the acquisition system.
Prior approaches to supporting mixed-domain and RF triggering functionality primarily target single-digitizer component systems, which limits the sample rate and bandwidth that can be acquired. To support a greater input frequency range in an acquisition system traditionally has required expensive RF oscillator and mixer components to down-convert the input signal in the analog domain prior to the ADC component. This type of system is still limited to the bandwidth and sample rate of a single ADC.
It would be desirable to have an acquisition technique that allows the acquisition to span wide bandwidths that exceed the bandwidth and sample rate supported by a single ADC component and allow real-time RF triggering on any frequency range within the wide bandwidth of the system in an efficient manner. It would also be desirable to distribute the digital down-conversion (DDC) function and related computations between multiple distributed time-interleaved acquisition components and reconstruct a coherent waveform in real-time to support RF trigger functionality.